International Journal of Molecular Ecology and Conservation, 2025, Vol.15, No.5, 249-259 http://ecoevopublisher.com/index.php/ijmec 25 2 3 Territoriality and Population Regulation 3.1 Territorial role in population density regulation Territorality, as a spatial competition mechanism, has a significant self-regulating effect on animal population density (Rueda et al., 2021). In highly territorial species, the number of breeding individuals that a habitat can accommodate is often limited by the number of territories that can be divided in that area. This phenomenon is also manifested in social animals such as wolves: Wolf packs occupy a fixed-size territory. Once the available space is insufficient, newborn cubs have to leave the pack and become wandering individuals when they grow up until they find a vacant territory (Sells et al., 2021). Territorial behavior not only limits the maximum density but also affects dynamics at low densities. Theoretical research shows that territorial spatial structure may bring about the Alli effect: when the population density is too low, lacking the interactive stimulation of neighboring individuals, territorial owners encounter unfamiliar invasions more frequently instead, the cost of territorial defense increases, resulting in further reduction of reproductive success and survival rate (Mayer et al., 2020). Model simulation also supports this complex effect: Population models of spatial structure show that territory competition can spontaneously generate multiple stable states and a minimum necessary population size, that is, if the number of individuals is lower than a certain threshold, the population is difficult to maintain (Alli effect) (Weiner et al., 2019). Empirical studies also show that territorial behavior does indeed play the role of a regulator in the actual population dynamics. For instance, in the field experiment of red squirrels, by supplementing food to enrich the resources in certain areas, the squirrels reduced their respective territories, accommodated more individuals, and the coexistence density increased (Berlusconi et al., 2025). Territoriality affects the distribution of reproductive opportunities through spatial exclusivity, thus becoming one of the important mechanisms for regulating the intrinsic density of a population. When conducting population dynamics prediction and management, considering the existence of territoriality can more accurately evaluate the population growth trend and density feedback effect (Marques et al., 2024). 3.2 The influence of territoriality on reproductive success rate Obtaining and defending a high-quality territory is usually one of the prerequisites for an animal to achieve reproductive success. In many species, only individuals with territory can successfully mate, build nests and raise offspring, while the "landless" without territory often lack reproductive opportunities (Rueda et al., 2021). Research shows that the reproductive success rate of territory owners is significantly higher than that of non-territory individuals: owning a territory is equivalent to having resources and the right to mate. Apart from whether reproduction occurs or not, the quality of the territory also affects the reproductive output. Rich in resources and vast in area, territories often offer more food and shelter, thereby benefiting the spouses and offspring of the landowners and achieving a higher reproductive success rate (Ord, 2021). A study on the white-browed robin (hypothetical species) found that male birds occupying high-quality territory had significantly higher numbers of chicks hatched and survival rates from their mates than those in low-quality territory breeding pairs (Lopez-peinado et al., 2024). Similar cases also exist in fish: Studies have found that in the Texas endemic Leon Springs pupfish, the territorial male fish protect the ovipositor by continuously patrolling (rather than simply attacking intruders), and eventually retain more eggs (Snekser et al., 2024). On the other hand, territoriality can also bring about cost trade-offs in reproduction. Continuous defense of territory requires time and energy, which may reduce the energy animals devote to foraging and caring for their young, thereby affecting reproductive input to a certain extent (Ord, 2021). 3.3 Territoriality and individual suitability Individual fitness refers to an individual's relative ability to pass on their genes to their offspring, which is usually determined by both survival and reproduction. Territorial behavior can enhance an individual's survival and reproductive success through multiple channels, thereby improving their fitness. Individuals who hold territory usually have more opportunities to obtain resources: an adequate and stable food supply helps maintain good physical condition and increases survival rates during the overwintering and breeding periods. Suitable territorial
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